Three dimensional tomographic fabric assembly

ABSTRACT

A fabric made by selective deposition modeling or fused deposition modeling, where the material is fed from at least one nozzle onto a moveable belt. The nozzle is moveable translationally and the spacing between the nozzle and the belt is adjustable. Flow through the nozzle and translational movement of the nozzle is controlled such that the nozzle dispenses the material in a controlled manner to form the fabric layer by layer.

This invention relates to industrial nonwoven fabrics and hasparticular, though not exclusive, relevance to nonwoven papermachinefabrics such as forming fabrics, press felts, dryer fabrics, through-airdryer (TAD) fabrics, hydroentanglement screens and transfer fabrics foruse in a papermachine. The fabrics of the invention also haveapplication as transfer/conveyor fabrics in machines other thanpapermachines and may be used, for example, as conveying fabrics, or asscreens for latex impregnation of conventionally air-laid materials, andfor support or formation screens used in melt blowing or spun bondednonwoven fabric manufacture.

Paper is conventionally manufactured by conveying a paper furnish,usually consisting of an initial slurry of cellulosic fibres, on aforming fabric or between two forming fabrics in a forming section, thenascent sheet then being passed through a pressing section andultimately through a drying section of a papermaking machine. In thecase of standard tissue paper machines, the paper web is transferredfrom the press fabric to a Yankee dryer cylinder and then creped, oralternatively on more modern machines a monofilament woven mesh dryerfabric conveys the web from the forming fabric to a through-air dryer,followed by a Yankee cylinder.

Papermachine clothing is essentially employed to carry the paper webthrough these various stages of the papermaking machine and tofacilitate water removal from the sheet in a controlled manner. In theforming section the fibrous furnish is wet-laid onto a moving formingwire and water is encouraged to drain from it by means of suction boxesand foils. The paper web is then transferred to a press fabric thatconveys it through the pressing section, where it is usually passesthrough a series of pressure nips formed by rotating cylindrical pressrolls or cylindrical press rolls and shoe press belts. Water is squeezedfrom the paper web and into the press fabric as the web and fabric passthrough the nip together. In the final stage, the paper web istransferred either to a Yankee dryer, in the case of tissue papermanufacture, or to a set of dryer cylinders upon which, aided by theclamping action of the dryer fabric, the majority of the remaining wateris evaporated.

Papermachine fabrics traditionally consist of a woven fabric. As thewarp and weft yarns interweave, a so-called “knuckle” is formed as theycross. These knuckles have a tendency to mark the paper sheet formed onthe fabric. This problem is particularly apparent at the wet end of thepapermachine where the sheet is still highly plastic. In recent years,various methods have been suggested for making nonwoven papermachinefabrics in order to eradicate the problem associated with knucklemarking, particularly for press and dryer section applications. Many ofthese have been impractical to manufacture commercially.

U.S. Pat. No. 3,617,442 describes a forming fabric comprising a sheet ofsynthetic, open-celled, flexible foam such as polyurethane. This isreinforced by a series of polyester cables, a coarse wire screen or athin flexible metal or plastic sheet. Such an arrangement, if evercommercialised, would exhibit poor wear resistance.

GB 2,051,154 relates to a so-called “link belt” in which a base fabricis formed from a series of interdigitated helices joined together bypintle wires. Link belts are only suitable for certain applications, dueto calliper and material restrictions.

U.S. Pat. No. 4,541,895 describes a papermakers' fabric made up of aplurality of nonwoven sheets laminated together to define a fabric orbelt. The nonwoven sheets are perforated by laser drilling. Such sheetsare composed of unoriented polymer material, and if produced in thefineness needed for papermaking applications, would lack sufficientdimensional stability to operate as endless belts on papermachines.

The subject invention of GB 2,235,705 describes a base fabric for pressfelts. Here an array of sheath core yarns of which the core has a highermelting point than the sheath, is fed in spaced parallel disposition toperipheral grooves of a pressed roller arranged in nip-formingrelationship with a press roll. The material of the sheath is melted asthe yarns move into and through the roller nip and excess melted sheathmaterial is forced into lateral and vacant circumferential grooves inthe roller to form structural members between adjacent yarns. A widebelt may be formed by joining similar strips together. A batt of fibresis subsequently needled to the base fabric so as to form a press felt.The base fabric provided in accordance with GB 2,235,705 has large landareas. Thus there is a lot of “dead” space which can result in theproduction of an uneven paper sheet. Also perforations through themesh-like base fabric extend straight through the fabric. This isundesirable for paper sheet formation, where controlled dewatering isrequired, especially during the delicate sheet forming phase.

GB 2,241,915 relates to a method of producing a papermaking fabric inwhich a layer of photopolymeric resin is applied to a moving band. Amoving, selectively transparent, mask is positioned above the resin andthe resin is irradiated through the mask to effect an at least partialcure of the parts of the resin layer in register with the transparentregions of the mask. After irradiation uncured regions of the resin areremoved by pressure fluid jets and final curing of the resin is effectedeither thermally or by means of flooding actinic radiation. Theforaminous sheet so formed may be reinforced with yarns or fibres. Onceagain holes extend straight through the fabric. This is undesirable forpaper sheet formation and additionally permits the occurrence of harmful“backwash” which comes from hydraulic pulses passing through the fabricfrom the machine side. The direct passage of these pulses disturbs thefragile cellulosic fibrous network.

GB 2,283,991 relates to papermachine clothing made from partially fusedparticles. A reinforcing structure is embedded within the structure.This papermachine clothing is suitable for pressing applications andpossibly special forming applications.

U.S. Pat. No. 5,501,824 describes an apparatus and method of makingthree-dimensional objects out of a modified wax, which becomes fluid onheating. The solid wax object may easily be damaged. The method wouldhave particular application in the production of small prototypes, whichare then generally embedded in foundry moulding sand to enable a metalcasting to be made. The prototypes are formed, on a vertically moveableplatform, by disposing the material in a controlled manner from anozzle. The nozzle and platform are moveable under the control of acomputer such that the material dispensed from the nozzle is in thecorrect location to build up the prototype in the manner illustrated ina CAD system connected to the computer. Support material for the desiredobject is constructed first during the method, where required, and islater removed.

U.S. Pat. No. 5,121,329 discloses a method of making a 3D object by whatis now called Fused Deposition Modelling.

The products made in accordance with U.S. Pat. No. 5,121,329 and U.S.Pat. No. 5,501,824 and other rapid prototyping or Free Form Fabricationmethods have generally been one-off prototypes which are generally rigidand have no function other than to aid the manufacture of an end productof similar dimensions, but which is made from a different material, forexample metal.

The use of Free Form Fabrication (FFF) technology in the manufacture ofpapermachine clothing and other industrial fabrics has not previouslybeen contemplated in that the potential of applying that technology toflat, wide, long flexible structures has not hitherto been considered.

According to a first aspect of the present invention there is provided amethod of making a fabric by Free Form Fabrication.

For the avoidance of doubt the term “Free Form Fabrication” as usedherein embraces so-called selective deposition modelling and so-calledfused deposition modelling. An example of selective deposition modellingis found in U.S. Pat. No. 5,501,824. An example of fused depositionmodelling is found in U.S. Pat. No. 5,121,329. The fabrics in accordancewith the invention have particular, although not exclusive, applicationin the manufacture of papermachine clothing. This technology has beenidentified as being ideally suitable for the manufacture of formingfabrics, base fabrics for press felts and dryer fabrics.

The term Free Form Fabrication used herein describes the formation of athree-dimensional object, tomographically layer by layer, in a stepwisefashion out of a material capable of physical transformation. This maybe achieved in a number of ways. In one approach (selective depositionmodelling, (SDM)) layers of fluid material are laid down, stepwise, indroplet form from an inkjet printing head, in the desired locations andare each solidified as they are laid down. In an alternative approach toselective deposition modelling, fused deposition modelling (FDM) isused. Here a monofilament feed yarn is melted, and then extruded, via amicro-extruder, in fine filament form via a head which can move in x, yand z directions, i.e. vertically and horizontally in two planes. Againlayers of fluid material are laid down stepwise in the desired locationsand are each solidified as they are laid down.

According to a second aspect of the present invention there is provideda method of making a fabric from a material comprising the followingsteps:—feeding material from at least one nozzle onto a moveable belt,wherein said nozzle is moveable for translational movement and thespacing between said nozzle and the belt is adjustable, and wherein flowthrough said nozzle and translational movement of said nozzle iscontrolled such that said nozzle dispenses the material in a controlledmanner to form the fabric layer-by-layer.

According to a third aspect of the present invention there is providedan apparatus for making a fabric from a material layer-by-layer, theapparatus comprising at least one nozzle and a moveable belt, the nozzlebeing operable to feed material onto the moveable belt, wherein thenozzle is moveable for translational movement and the spacing betweenthe nozzle and the belt is adjustable, and wherein flow through saidnozzle and translational movement of said nozzle is controlled such thatsaid nozzle dispenses the material in a controlled manner to form thefabric layer by layer.

For SDM the nozzles are ideally provided in at least one feed head so asto provide a “multi-jet” arrangement, a number of nozzles being providedin each feed head. A plurality of feed heads would conventionally beused with selective deposition modelling. The flow through the nozzle isquantised; i.e. droplets are projected rather than there being acontinuous stream of fluid. The nozzles together might typically bedispensing about 12,000 drops (pico litre size), per second. With fuseddeposition modelling one nozzle is generally provided for eachmicro-extruder head. The material is extruded from the nozzles.

The method of the invention, by both SDM and FDM, facilitates themanufacture of a wide variety of fabric configurations. A wide varietyof foraminous fabrics may be made having any aperture size, shape anddistribution. The aperture size, shape and/or distribution may bedeliberately varied, within desirable tolerances, throughout (or atleast in the paper support surface of) the fabric although the porosityof the fabric should be kept as uniform as possible. By providing arandom distribution of hole shapes, sizes and location in the papersupport surface of the fabric the undesirable periodicity associatedwith regular weave structures is avoided.

The fabrics of the invention ideally comprise an array of yarnsextending in the intended running direction thereof, on a machine.Consequently drawn yarns, to prevent extension, are preferably added tothe built up fabric. These yarns provide strength in the machinedirection. The yarns are preferably monofilaments or multifilaments andare ideally made from any of the following materials: steel, polyester,polyamide, polyolefin, PPS, PEEK, para-aramid or from inorganicmaterial, for example glass or basalt. The yarns are preferably at leastpartly, and ideally fully, encapsulated in the machine direction landsof the nonwoven fabric as built up in the method of the invention.

Ideally the aforesaid material for making the fabric is normally (atroom temperature (20° C.)) in a solid state and preferably is mademolten by heating. In such circumstances the droplets of material cooland thus solidify as they are deposited.

A preferred material for making the fabric, by selective depositionmodelling, comprises a low viscosity (2-200 Centipoise, more preferably5-40 Centipoise, measured at room temperature (20° C.)) meltablepolymeric material. The apparatus for use in the method of the inventionmay be InVision Si2 of 3D Systems, which is for use in the manufactureof items by selective deposition modelling using electrically activatedpiezo crystals. Here two polymers are projected out of different nozzlesof the same feed head. One polymer is the true building material and theother is a support or scaffolding material, which may comprise, forexample, a modified wax. The latter material provides temporary supportfor subsequent layers of building material which may later be removedthermally, possibly by the application of hot water.

A preferred material for making the fabric by selective depositionmodelling would comprise a meltable polymer which solidifies on cooling.Such polymers are often referred to as “phase change materials”.Suitable thermoplastic materials for the construction of the fabric byselective deposition modelling include, but are not limited to, any ofthe following either alone or in combination:—polyamides, co-polyamides,polyesters, co-polyesters, amide esters, olefin resins, urethanes, amideurethanes and sulphones.

An alternative preferred material for making the fabric by selectivedeposition modelling comprises a curable material, such as a radiationcurable material. For example, a UV curable resin may be used, such asan acrylate-based UV curable resin, which material solidifies onexposure to UV light. The curable material may be delivered to theapparatus in the form of a relatively viscous gel which may be heated tolower its viscosity to a suitable level to enable droplets thereof to beformed for projection out of the nozzles, which in the case of theInVision Si2 apparatus comprise piezo crystal controlled nozzles.Suitable monomers or oligomers, which solidify under the influence of UVlight of suitable wavelength, include, but are not limited to, any ofthe following, either alone or in combination: epoxy acrylates,polyester acrylates, silicone acrylates and urethane acrylates.Cross-linking of such materials may be promoted using a compatible photoinitiator. The rate of cross-linking may, if desired, be increased usinga synergist, such as an acrylated amine.

Heating of the UV curable resins may not in every case be necessary foreffective production of the fabric by selective deposition modelling.However, it may nevertheless be desirable that the UV curable resin beheated in order to optimise the viscosity of the resin for projectionthrough the nozzles of the apparatus.

With regard to preferred support or scaffolding materials, thesecomprise hot melt resins or waxes, said materials having melting pointslower than the polymer(s) comprising the true building, or matrix,material.

In fused deposition modelling the true building, or matrix, material ispreferably supplied to the dispensing head in the form of a flexiblestrand of solid material from a supply source, such as a reel or rod.This material is heated above its solidification temperature (Tm) by aheater and then dispensed by extrusion and applied as a fluid.

Suitable thermoplastic materials for use in making the fabric by fuseddeposition modelling include, but are not limited to, any of thefollowing either alone or in combination:—polyesters, polyamides, highmolecular weight polyethylenes, polyphenylene sulphide, thermoplasticpolyurethanes and PEEK.

In some embodiments of the invention the resin for forming the fabricmay be supplemented with a second resin or other material, which acts asa support structure for the manufacture of the fabric. This second resinor other material is ideally dissolvable or removable thermally at atemperature that does not affect the stability of the fabric. Suitableexamples of such materials include any of the following either alone orin combination:—PEO (poly(2-ethyl-2-oxazoline)), polyvinyl alcohol,polyethylene oxide, methyl vinyl ether, polyvinyl pyrrolidone-basedpolymers, maleic acid-based polymers and alkali-soluble base polymerscontaining carboxylic acid and plasticiser.

The fabric filaments embodied in the structure, which are built upduring the process may be of any cross-section, e.g. round, square ortriangular.

The method of the invention may be used to form complicated fabricstructures, with filaments of end sections, which cannot be utilised inconventional weaving. For example the fabric may comprise lands,filaments or strands which are triangular in cross-section. Yarns withsuch end sections would be liable to twisting or distortion duringinsertion into a woven fabric on a loom.

In one embodiment apertures are provided in the support surface havingdimensions which would accord to those of current woven fabrics.However, fabrics having smaller apertures may be made in accordance withthe method of the invention. Typically the notional diameter of theapertures would be in the range from 100 μm to 800 μm.

In order that the present invention may be more readily understoodspecific embodiments thereof will now be described by way of exampleonly with reference to the accompanying drawings in which:

FIG. 1 is a diagram of one apparatus for making a nonwoven fabric inaccordance with the present invention;

FIG. 2 is a perspective view of part of one nonwoven fabric made inaccordance with the present invention;

FIG. 3 is a side elevation of the nonwoven fabric of FIG. 2;

FIG. 4 is a diagrammatic illustration of the underside of the nonwovenfabric of FIGS. 2 and 3 shown during various stages of construction;

FIG. 5 (including FIGS. 5 a and 5 b) shows alternative methods ofproducing a fabric in accordance with the invention from a series ofpanels extending in the cross-machine direction each made using theapparatus of FIG. 1;

FIG. 6 shows a method of producing a fabric in accordance with theinvention from a series of panels extending in the machine directioneach made using the apparatus of FIG. 1;

FIG. 7 is a perspective view of a second nonwoven fabric made inaccordance with the present invention;

FIG. 8 is a side elevation of a third nonwoven fabric made in accordancewith the present invention;

FIG. 9 is a perspective view of a fourth nonwoven fabric made inaccordance with the present invention;

FIG. 10 is a perspective view of a further nonwoven fabric made inaccordance with the present invention; and

FIG. 11 is a diagram of a second apparatus for making a nonwoven fabricin accordance with the present invention.

Referring to FIG. 1 an apparatus 10 for making a nonwoven formingfabric, without the disadvantage of knuckles formed by yarninterlacings, by SDM in accordance with the present invention comprisesa plurality of feed heads 13 mounted in such a manner as to facilitatetranslational movement in both the X and Y directions as well asvertically in the Z direction. In this embodiment each feed head 13typically comprises about 450 dispensing nozzles (not shown), althoughmore may be used. In the Y direction the feed heads must be capable ofsufficient travel such that material for making the fabric may bedeposited from at least one of the nozzles of a feed head at anyposition in the Y-axis between the edges of the fabric beingmanufactured on the belt. Ideally the limitation of travel of adjacentfeed heads 13 is such that the areas over which adjacent feed heads 13may pass overlap. Vertical movement in the Z-direction of up to about 5mm is required to allow for continued precision of droplet deposition asthe thickness of the product being made gradually increases.

Each feed head 13 is connected via a first flexible pipe 15 to areservoir (not shown) of heated fluid polymeric material that isnormally solid in ambient conditions and which melts when sufficientlyheated. The first flexible pipe branches off to finer tubes each ofwhich is coupled to an individual feed head. Within each feed headheated fluid polymeric material is fed via individual channels toindividual nozzles. The viscosity of the molten material is preferablyin the range from 2-200 Centipoise, more preferably 5-40 Centipoise,measured at room temperature (20° C.). An ionic resin may be used, suchas SURLYN (Trade Mark) as marketed by Du Pont. In accordance with thetechniques described in U.S. Pat. No. 5,501,824 the flow of polymericmaterial via a valve at the end of the nozzle 13 is controlled by acomputer. That computer is connected to a CAD system on which is locateda representation of the section of the nonwoven fabric being reproducedin 3D form by the apparatus.

In use the section or panel of nonwoven fabric being reproduced isformed on an endless belt 14 tensioned between two rollers. The beltwould, generally speaking, comprise a fabric, optionally coated with anon-stick coating such as PTFE.

Generally speaking manufactured material would be fed from the endlessbelt 14 to a storage roll. Alternatively an endless product may bemanufactured around the circumference of the belt 14.

A representation of the panel is provided on the CAD system. The controlcomputer effectively slices the CAD representation into a plurality ofvirtual layer representations, which are together known as a buildingrepresentation. The control computer uses the data on the CAD system toreproduce stepwise layer by layer of the panel of the nonwoven fabric onthe belt 14 by appropriate application of the molten polymeric material.As drops of polymeric material are deposited onto the belt, or as theprocess progresses, onto previously solidified material, there is arapid heat loss and the drops solidify. Accurate location and flow ofthe polymeric material is achieved by a combination of controlling flowof the polymer through the nozzles 13 and the precise ejection ofdroplets by controlled firing of the piezo electric crystals within thefeed head as well as, movement of the feed head 13 in the X, Y and Zdirections. In the formation of a single section or panel of the fabricthe method used is much the same as that described in U.S. Pat. No.5,501,824, except in that a moveable belt 14 is used in place of aplatform. Furthermore, strength-providing yarns are generally includedin the fabric.

Once the panel is constructed in accordance with the representation onthe CAD system, the belt will then advance in a controlled manner to theposition to which additional material is to be added to form the nextpanel or panels.

After a layer of panels has been formed it may be advantageous to fillin any hollow areas in that layer with a second material in order toprovide support to the next layer. This is a so-called “temporary laydown phase”. This second material can be removed once manufacture iscomplete, for example by washing or melting when the second material hasa lower melting point than the material from which the fabric is made.In order to dispense this second material certain nozzles of thedispensing heads would be connected via a second flexible pipe to areservoir of such material and not to the fabric-forming material.

Referring to FIGS. 2 and 3 part of a nonwoven fabric 20, in accordancewith the invention, is illustrated. This comprises a fine planar uppergrid 21 secured to the tips of a series of parallel cross-machinedirection lands 22, which, in this embodiment, are triangular insection. The flat bases of these triangular lands 22 are secured to anarray of parallel machine direction lands 23 which are square in crosssection. The width of the paper contacting lands in the grid 21 istypically in the order of 0.1 mm. The depth of this layer is typicallyabout 0.1-0.2 mm. The dimensions of the apertures defined by the landsare preferably at least 100 microns by 100 microns, though the holeshapes need not be rectangular.

It is noted that the position of the CMD lands 22 relative to the paperformation grid 21 may be varied. For example, two triangular lands 22might cover or straddle the holes. Many variations are possible in theinterests of providing optimum dewatering efficiency and performance.

Videomicroscope at magnification of 55× shows that hemispheres ofpolymer; i.e. micro-globules are produced on the surface of the lands inthat the lands are built up from globules of polymer. Thesemicro-globules help provide for good sheet release without resulting inmarking of the paper formed on the surface of the structure.

In some circumstances it may be desirable to provide a non-planarsupport surface at a macroscopic level. For example, this may be usefulin providing sheet release with difficult pulp mixtures. Such a surfacecould be conferred upon the fabric by means of a non-planar receivingbelt. This could be used to provide an, at least partially, undulatingfabric surface of the type described in U.S. Pat. No. 5,847,102.

It is possible, by providing a flexible pipe from the feed head to anadditional reservoir, to change the polymeric constituents as thestructural build approaches completion on the paperside, such that thepaperside surface is made of a different material to the wearside. Apolymer containing fluorine could, for example, be added in the finalstages of manufacture, which would be more hydro/oleophobic than itspreceding layers. Thus the method of the invention provides for themanufacture of bi or even multi component structures so as to providethe completed fabric with the required characteristics.

Referring to FIG. 4 a monofilament yarn 24 of maximum diameter 0.2 mm isencapsulated in each of the machine direction lands 23 below the fabricsupporting grid 21 so as to provide strength in the running direction ofthe fabrics when in use. This maximum diameter may be appropriate forforming fabrics. For other fabrics other diameters might be appropriate.For example, for dryer fabrics a maximum diameter of 0.6 mm may beappropriate. These monofilament yarns could be pre-assembled in spiralfashion during manufacture. The laying down of polymeric material wouldtake account of the very slight sideways movement of the yarns. Anelectronic follower could be used to establish an exact reference pointbefore the onset of printing each panel.

In FIG. 4 the sequence of fabric build (a) to (c), at the roll side ofthe fabric, shows how a semi-circle is created to allow yarn to beintroduced at (a). Thereafter in (b) and then (c) the jet printing ofmaterial builds up around the yarn to eventually fully encapsulate it.

The strength providing yarns in the machine direction need not bemonofilaments. For example, fine multifilament yarns could be used (e.g.dtex 500). The yarns may, for example, be made of steel, polyester,polyamide, polyolefin, PPS, PEEK, para-aramid or from inorganicmaterial, e.g. glass or basalt. Bonding to the polymeric surface may beenhanced by suitable surface treatments such as tie-coats or surfaceactivation such as plasma treatment.

As an alternative or in addition to incorporating monofilament yarns inthe machine direction lands, a nonwoven fabric of the invention may besecured on its underside, to a conventional fabric such as a wovenfabric or possibly to a further nonwoven fabric or knitted fabric. Thefabric of the invention can also be secured at its topside to a finewoven forming fabric to yield specific formation properties as desiredor to nonwoven fibrous batts.

The fabric would preferably be built up in endless form to avoid seamingproblems as are commonly encountered in the art when making seamedbelts, particularly for use in papermaking. Such problems are moreapparent for belts used at the wet end of the papermachine; i.e. formingfabrics. Here differential permeability between the seam and the rest ofthe belt can cause unacceptable marking of the paper sheet as formed inthe seam area of the belt. Considerable time and effort and thus costare involved in attempting to minimise these problems.

The fabric has particular application as a forming fabric in that itprovides a fine support network for the paper furnish whilst at the sametime allowing for controlled drainage, as aided by the orientation,number and cross-section of the created “yarns” or filaments within thefabric. The adoption of at least some filaments that are triangular(including substantially triangular), or other yarns having a goodhydrodynamic shape, is valuable in this respect.

It will be appreciated that known Free Form Fabrication techniques haveresulted in the formation of a non, or partially, durable temporaryproduct of relatively small dimensions. The apparatus previously used toproduce such products is not of sufficient scale to generate fabrics inaccordance with the invention that might typically be 11 m by 30 m. Theinvention proposes to build up the fabric from a number of filamentsextending in both the machine direction and cross machine direction.This is achieved using an array of multi-jet heads, which effectivelyprint a series of panels in a row, ideally in the cross-machinedirection. This is illustrated in FIG. 5. Here the heads are programmedby the computer to print panels 25 with multiple tongue and groovecombinations, alternative arrangements being shown in FIGS. 5 a and 5 b.In FIG. 5 b some tongues are chosen to be longer than others to enhancepanel bonding. In both FIGS. 5 a and 5 b the panels are made up stepwiseby a series of layers Z₁-Z₅.

The growth of the fabric in the machine direction is achieved by forminga panel, or in the case of a multi-head manufacturing assembly a seriesof panels, onto the moveable belt 14.

With reference to FIG. 6 it is envisaged that the support belt for thegrowing foraminous polymer assembly could possibly advance continuouslybut slowly forwards, but generally speaking and preferably, the beltwould be arrested in a static state whilst a full panel consisting ofdiscrete layers Z₁-Z₄ is built up. This intermittent movement of thebelt provides for more accurate delivery of the polymeric material.Another benefit is that maintenance of the polymer feed heads can takeplace whilst the belt is in a static state without detriment to anypartially manufactured belt on the machine. When the complete panel 25(i) has been constructed the belt then advances for the commencement ofthe following panel 25 (ii). This process is repeated until the completebelt has been manufactured in both length and width directions.

Because of the accuracy of the micro control system of the process,incomplete panels, both in the machine direction and the cross machinedirection can be built-up. The lack of completion makes for betterintegration with adjacent panels when they are started as the processingprogresses.

In the running direction an incompleted step will be left at the rear ofthe panel previously built up. If, for the sake of example, a foraminousbelt is derived from four layers Z₁, Z₂, Z₃, Z₄, the complete panel willcontain 100% of layers Z₁ and Z₂. However, layers Z₃ and Z₄ may eitherbe the same or selected to be different. The incomplete areas, Z₃ and Z₄are then filled in when the following panel is built up. The benefit ofthis split-level assembly is likely to be the derivation of abetter-integrated fabric.

It can be seen that the laid-down area of all four layers is identical.Layers Z₄ and Z₃ are simply displaced in a forwards direction relativeto Z₂ and Z₁. The overlap situation created aids inter panel bonding andcontributes to better production uniformity.

In FIG. 7 in a further fabric 30 in accordance with the invention thetips 31 of the triangular cross-machine lands 32 have been, where theycontact the grid 33 located thereupon, modified to create flat areas 34.These create a large contact area for bonding to the upper grid 33. Thesame procedure would be adopted for filaments generated with alternativeend sections.

Referring to FIG. 8 a further embodiment 35 of the nonwoven fabric ofthe invention is illustrated. Here the triangular end sectionintermediate layer has been replaced with angled ribs 36. This may serveto better control drainage.

In the embodiment illustrated in FIG. 9 a sheet 37 comprising an arrayof perforations of random size and shape is used to support the paperweb, although the overall integrated (or average) pore size over a givenarea ideally remains uniform. By providing randomised topographicalperforation distribution in the x-y plane, regular patterns of aperturesfrom the forming fabric, which are conventionally replicated as anegative in the paper product, are not so replicated. Thus no regularpattern is perceptible, this so-called periodicity being considered tobe undesirable in papermaking.

The fabric of FIG. 9 is made in a like manner to the other fabrics ofthe invention as previously described. It is relatively straightforwardto build up a fabric in which a support sheet layer having a randomdistribution of holes is integral with regularly spaced lands locatedtherebelow. A temporary lay down phase of wax or the like is used tofill the gaps between the lands below the intended location of the sheetand the sheet is built up over the lands and temporary filler material.This temporary material is removed, for example by washing or melting,after fabric manufacture is complete.

The embodiment of FIG. 10 is similar to that shown in FIG. 9 except thatthe cross-machine direction triangular lands 38 are curved so as toprevent them from encroaching upon the perforations in the paper pulpsupport layer 39 which is similar to that described with reference toFIG. 9.

Referring to FIG. 11 a further apparatus 40 for making a nonwoven dryerfabric in accordance with the present invention comprises a plurality offeed heads 41 mounted in such a manner as to facilitate translationalmovement in both the X and Y directions as well as vertically in the Zdirection. The apparatus 40 is similar to that disclosed in relation toFIG. 1 except that this apparatus is designed to manufacture a fabric byfused deposition modelling.

Therefore each feed head 41 comprises two sets of dispensing nozzles,one of which receives PPS plastics filament of about 1/16 inch diameterfrom a feed reel. Alternatively plastics pellets might be fed from ahopper rather than a filament. The other set of dispensing nozzles isfed a filament of a second, preferably water soluble acrylic polymer,material from a second feed reel. Again, alternatively this material maybe supplied via a hopper. The first plastic filament is used tomanufacture the fabric, whereas the second filament is used to form the“temporary lay down phase” as discussed with reference to FIG. 1.

In use the plastic filaments are fed to the extrusion nozzles where theyare heated so as to melt and thus fluidise the plastic. Extruded flowthrough each nozzle is controlled by a valve mechanism at the nozzle.The emerging extrudate is continuous until flow is terminated via thevalve to allow the feed head to jump a deposition gap before the flow isreinstated.

Each feed head comprises two dispensing nozzles, although more may beused. Generally speaking the FDM apparatus would comprise 4 to 40, andmore preferably 10 to 30, feed heads. The nozzles are movable in the X,Y and Z directions. In the Y direction the feed heads must be capable ofsufficient travel such that material for making the fabric may beextruded from at least one of the nozzles of a feed head at any positionin the Y-axis between the edges of the fabric being manufactured on thebelt. Ideally the limitation of travel of adjacent feed heads is suchthat the areas over which adjacent nozzles may pass overlap. Verticalmovement in the Z-direction of up to about 5 mm is required to allow forcontinued precision of deposition of extruded material as the thicknessof the product being made gradually increases. In accordance with thetechniques described in U.S. Pat. No. 5,501,824 the flow of polymericmaterial via a valve at the end of each nozzle is controlled by acomputer where the work piece to be made is digitised and converted intoan STL (singular tessellated language) file. The computer is connectedto a CAD system on which is located a representation of the section ofthe nonwoven fabric being reproduced in 3D form by the apparatus.

In use the section or panel of nonwoven fabric being reproduced isformed on an endless belt 42 tensioned between two rollers. The belt 42would, generally speaking, comprise a fabric, optionally coated with anon-stick coating such as PTFE.

A representation of the panel is provided on the CAD system. The controlcomputer effectively slices the CAD representation into a plurality ofvirtual layer representations, which are together known as a buildingrepresentation. The control computer uses the data on the CAD system toreproduce stepwise layer by layer of the panel of the nonwoven fabric onthe belt 42 by appropriate application of a thin bead of extruded moltenpolymeric material to form each layer. As polymeric material is extrudedonto the belt, or as the process progresses, onto previously solidifiedmaterial, there is a rapid heat loss and the extruded plastic solidifiesimmediately bonding with any previously laid down material. Accuratelocation and flow of the polymeric material is achieved by a combinationof controlling flow of the polymer through the nozzles in the feed head41 via valves and movement of the feed head 41 in the X, Y and Zdirections. In the formation of a single section or panel of the fabricthe method used is much the same as that described in U.S. Pat. No.5,121,329, except in that a movable belt 42 is used in place of aplatform. Furthermore, strength-providing yarns are generally includedin the intended machine direction of the fabric.

Once the panel is constructed in accordance with the representation onthe CAD system, the belt will then advance in a controlled manner to theposition to which additional material is to be added to form the nextpanel or panels.

After a layer of panels has been formed it may be advantageous to fillin any hollow areas in that layer with a second material in order toprovide support to the next layer. This is a so-called “temporary laydown phase”. This second material can be removed once manufacture iscomplete, for example by dissolving, washing or melting when the secondmaterial has a lower melting point than the material from which thefabric is made. In order to dispense this second material certainnozzles of the dispensing heads would be connected via a second flexiblepipe to a reservoir of such material and not to the fabric-formingmaterial.

The entire system is ideally contained within a heated enclosure, whichis held at a temperature just less than the melting point of theplastics being extruded. Thus only a small amount of energy needs to besupplied by the extrusion nozzle to cause the plastics to melt.

The method of manufacture using fused deposition modelling and theapparatus shown in FIG. 11 may be used to manufacture any of thestructures made in accordance with the apparatus of FIG. 1 andillustrated in FIGS. 2 to 4 and 7 to 10. Likewise the apparatus may beused to manufacture panels as shown in FIGS. 5 and 6.

It is to be understood that the above described embodiment is by way ofillustration only. Many modifications and variations are possible.

1. A method of making a fabric from a material comprising the steps of:feeding material from at least one nozzle onto a moveable belt, whereinsaid nozzle is moveable for translational movement and the spacingbetween said nozzle and the belt is adjustable, and wherein flow throughsaid nozzle and translational movement of said nozzle is controlled suchthat said nozzle dispenses the material in a controlled manner to formthe fabric layer-by-layer.
 2. The method of claim 1, wherein a pluralityof the at least one nozzle are provided in a feed head.
 3. The method ofclaim 1, wherein a plurality of the at least one nozzle are provided ina plurality of feed heads.
 4. The method claim 1, wherein the method ofmanufacturing the fabric comprises selective deposition modeling.
 5. Themethod of claim 1, wherein the flow of material through the nozzle isquantized.
 6. The method of claim 5, wherein the at least one nozzledispenses about 12,000 drops per second.
 7. The method of claim 1,wherein the material is a meltable polymeric material having a viscosityin the range from 2 to 200 Centipoise measured at 20° C.
 8. The methodof claim 7, wherein the material is a meltable polymeric material havinga viscosity in the range from 5 to 40 Centipoise measured at 20° C. 9.The method of claim 1, wherein the material is at least one ofpolyamides, co-polyamides, polyesters, co-polyesters, amide esters,olefin resins, urethanes, amide urethanes and sulphones.
 10. The methodof claim 1, wherein the material comprises a radiation curable material.11. The method of claim 10, wherein the material comprises a UV curablematerial.
 12. The method of claim 11, wherein the UV curable material isat least one of epoxy acrylates, poltester acrylates, silicone acrylatesand urethane acrylates.
 13. The method of claim 1, further comprisingfeeding from at least one nozzle, a temporary support medium forproviding temporary support to said material during manufacture of thefabric layer by layer.
 14. he method of claim 13, further comprising thestep of removing the temporary support medium.
 15. The method of claim13, wherein the temporary support medium comprises a material selectedfrom hot melt resins and waxes.
 16. The method of claim 1, wherein themethod of manufacture of the fabric comprises fused deposition modeling.17. The method of claim 16, wherein the material is extruded from atleast one of the nozzles.
 18. The method of claim 16, wherein thematerial is at least one of polyesters, polyamides, high molecularweight polyethylenes, polyphenylene sulphide, thermoplasticpolyurethanes and PEEK.
 19. The method of claim 16, wherein saidmaterial is fed to the nozzle as a flexible strand of solid material.20. The method of claim 16, further comprising the step of providing atemporary support medium for providing temporary support to saidmaterial during manufacture of the fabric layer by layer.
 21. The methodof claim 20, further comprising the step of removing the temporarysupport medium.
 22. The method of claim 20, wherein the temporarysupport medium comprises at least one of poly(2-ethyl-2-oxazoline),polyvinyl alcohol, polyethylene oxide, methyl vinyl ether, polyvinylpyrrolidone-based polymers, maleic acid-based polymers andalkali-soluble base polymers containing carboxylic acid and plasticiser.23. The method of claim 1, wherein means are provided for feeding anarray of machine direction yarns into the fabric.
 24. A method of makinga fabric by Free Form Fabrication.
 25. The method of claim 1, whereinthe fabric is papermachine clothing.
 26. An apparatus for making afabric from a material layer-by-layer, the apparatus comprising: atleast one nozzle and a moveable belt, the nozzle being operable to feedmaterial onto the moveable belt, wherein the nozzle is moveable fortranslational movement and the spacing between the nozzle and the beltis adjustable, and wherein flow through said nozzle and translationalmovement of said nozzle is controlled such that said nozzle dispensesthe material in a controlled manner to form the fabric layer by layer.27. The apparatus of claim 26, wherein a plurality of nozzles areprovided in a feed head.
 28. The apparatus of claim 26, wherein theapparatus comprises a plurality of feed heads.
 29. The apparatus ofclaim 26, wherein the apparatus manufactures the fabric by selectivedeposition modeling.
 30. The apparatus of claim 26, wherein the flowthrough the at least one nozzle is quantized.
 31. The apparatus of claim30, wherein the at least one nozzle dispenses about 12,000 drops persecond.
 32. The apparatus of claim 26, wherein the material is ameltable polymeric material having a viscosity in the range from 2 to200 Centipoise measured at 20° C.
 33. The apparatus of claim 32, whereinthe material is a meltable polymeric material having a viscosity in therange from 5 to 40 Centipoise measured at 20° C.
 34. The apparatus ofclaim 26, wherein the material is at least one of polyamides,co-polyamides, polyesters, co-polyesters, amide esters, olefin resins,urethanes, amide urethanes and sulphones.
 35. The apparatus of claim 26,wherein the material comprises a radiation curable material.
 36. Theapparatus as claimed in claim 35, wherein the material comprises a UVcurable material.
 37. The apparatus of claim 36, wherein the UV curablematerial is at least one of epoxy acrylates, poltester acrylates,silicone acrylates and urethane acrylates apparatus manufactures thefabric by selective deposition modeling.
 38. The apparatus of claim 26,further comprising at least one second nozzle for distributing temporarysupport to said material during manufacture of the fabric layer bylayer.
 39. The apparatus of claim 38, wherein said apparatus comprisesmeans for removing the temporary support material.
 40. The apparatus ofclaim 38, wherein the temporary support medium comprises a materialselected from hot melt resins or waxes.
 41. The apparatus of claim 26,wherein the apparatus manufactures the fabric by fused depositionmodelling.
 42. The apparatus of claim 41, wherein the material isextruded from the at least one nozzle.
 43. The apparatus of claim 41,wherein the material is at least one of polyesters, polyamides, highmolecular weight polyethylenes, polyphenylene sulphide, thermoplasticpolyurethanes and PEEK.
 44. The apparatus of claim 41, wherein saidmaterial is fed to the at least one nozzle as a flexible strand of solidmaterial.
 45. The apparatus of claim 41, wherein a further supportmaterial is fed via at least one second nozzle for providing temporarysupport to said material during the manufacture of the fabric layer bylayer.
 46. The apparatus of claim 45, wherein said apparatus comprisesmeans for removing the temporary support material.
 47. The apparatus ofclaim 45, wherein the temporary support medium comprises at least one ofpoly(2-ethyl-2-oxazoline), polyvinyl alcohol, polyethylene oxide, methylvinyl ether, polyvinyl pyrrolidone-based polymers, maleic acid-basedpolymers and alkali-soluble base polymers containing carboxylic acid andplasticiser.
 48. The apparatus of claim 26, wherein the apparatuscomprises means for feeding an array of machine direction yarns into thefabric.